Each frame, a gradually increasing value between 0 and 24 is output, but you’re summing them, which is why your total figure is going crazy. You need to plug the truncate directly into the ‘set’ without using the + node.
Then it will work, but I think you’ll find it will jump one hour each second over 24 seconds ( that’s what your timeline says ).
Is it possible to set the plugin with a float? ( much better ).